A conventional telecommunications network includes two distinct communication pathways or subnetworks—a voice network and a signaling network. These two networks function in a cooperative manner to facilitate calls between users. As implied by its name, the voice network handles the transmission of voice (or user data) information between users. The signaling network has a number of responsibilities, which include call setup, call teardown, and database access features. In simple terms, the signaling network facilitates the dynamic linking together of a number of discrete voice-type communication circuits such that a voice-type connection is established between a calling and a called party. Additionally, the signaling network provides a framework through which non-voice-related information may be transported, with this data and transport functionality being transparent to the users. This signaling technique is often referred to as out-of-band signaling, where the term “band” implies voice band.
The signaling protocol most commonly employed in communication networks around the world is the signaling system 7 (SS7) protocol. From a hardware perspective, an SS7 network includes a plurality of SS7 nodes, generically referred to as signaling points (SPs) that are interconnected using signaling links, also referred to as SS7 links. At least three types of SPs are provided in an SS7 network: service switching points (SSPs), signal transfer points (STPs) and service control points (SCPs). Within an SS7 signaling network, each SP is assigned an SS7 network address, which is referred to as a point code (PC).
An SSP is normally installed in Class 4 tandem or Class 5 end offices. The SSP is capable of handling both in-band signaling and SS7 signaling. An SSP can be a customer switch, an end-office, an access tandem and/or a tandem. An STP transfers signaling messages from one signaling link to another. STPs are packet switches and are generally installed as mated pairs. Finally, SCPs control access to databases, such as 800 number translation databases, 800 number carrier identification databases, calling card verification databases, etc.
Signaling links are transmission facilities used to connect SPs. Conventional signaling links are dedicated bidirectional facilities operating at 56 kbps in the U.S. and Canada and at 64 kbps when clear channel capability is deployed. Normally, every link has a mate for redundancy and enhanced network integrity.
Although the SS7 protocol was devised to ensure consistent and reliable communication across a signaling network infrastructure, it has proven to be the case that most countries have chosen to implement slightly different versions of the protocol. For instance, in the United States, an American National Standards Institute (ANSI) version of the SS7 protocol is employed. In Europe an International Telecommunications Union (ITU) version of the SS7 protocol is employed. In Europe, different countries may utilize different versions of ITU SS7. Such protocol variations pose significant problems for network operators attempting to provide international connectivity.
The goal of international connectivity is further complicated by the fact that telecommunications networks in different countries use the same point codes. That is, although a given SS7 point code must be unique within a given country's signaling network, there is no prohibition on using the same point code in another country's signaling network. This duplicate point code usage problem is particularly prevalent in the European telecommunications market.
In an effort to circumvent the duplicate point code usage problem, the ITU introduced a dual addressing scheme. This dual addressing scheme essentially defines two SS7-based protocols for use within a signaling network, a national (ITU-N) protocol and an international (ITU-I) protocol. Simply put, ITU-N point codes are 14-bit values that must be unique within a particular national signaling network but may be simultaneously assigned to SS7 nodes residing in other national networks. ITU-I point codes are also 14-bit values that must be universally unique. That is, no two SS7 nodes connected to an ITU international network may have the same ITU-I point codes.
FIG. 1 is a network diagram illustrating an example of the ITU-I and ITU-N point code scheme. The example illustrated in FIG. 1 includes a French ITU-based SS7 signaling network 100 and an Italian ITU-based SS7 signaling network 102. French network 100 includes a signal transfer point 104, a signaling point 106, and a signaling point 108. Similarly, Italian network 102 includes a signal transfer point 110, a signaling point 112, and a signaling point 114.
The French and Italian signaling points may be connected to their respective STPs via SS7 signaling links. The French and Italian STPs are connected via an SS7 signaling link. As such, all signaling between these two national networks takes place via the two STPs. That is, a French signaling point cannot directly signal an Italian signaling point. Instead, a French signaling point must formulate a signaling message that is transmitted to French STP 104 and subsequently routed to Italian STP 110, which transmits the message to the intended Italian signaling point. It will be appreciated that the French and Italian STPs serve to effectively isolate their respective networks from each other. From an ITU-N (national) message routing standpoint, French STP 104 is only provisioned with rules for routing messages within the French national network. The French STP has no knowledge and no need for knowledge of Italian national routing rules. This is the case because the ITU-I (international) protocol standard requires that any French signaling point intending to communicate with an Italian signaling point must generate and transmit an ITU-I signaling message addressed to the ITU-I point code of the intended Italian signaling point. In such an inter-network communication scenario, an ITU-N signaling message addressed to an ITU-N point code cannot be directly routed between two national networks. Rather, messages transmitted between networks must use ITU-I point codes.
As further indicated by the example illustrated in FIG. 1, each signaling point in the French and Italian networks is assigned both an ITU-N point code and an ITU-I point code. That is, French node 106 is assigned an ITU-N point code of 247 and an ITU-I point code of 5-0-1. Italian node 112 is assigned an ITU-N point code of 247 and an ITU-I point code of 5-0-3. Given the existing ITU dual protocol addressing scheme it would be difficult for an international network operator to implement a single STP (or mated STP pair) to simultaneously serve multiple national networks. That is, a single STP tasked with simultaneously routing ITU-N (national) traffic associated with two (or more) national networks would likely encounter signaling messages from one national network that are addressed to a point code that is also being used in the other national network. This would be the case for messages destined to either French signaling point 106 (French ITU-N point code: 247) or Italian signaling point 112 (Italian ITU-N point code: 247). Such duplicate point code routing scenarios present significant problems for STP routing nodes and their operators. Again, the problem is that a single STP directly coupled to SPs with duplicate point codes in two different national networks would have significant difficulty determining to which national network a message should be routed. In addition to message routing difficulties, network management in such a duplicate point code scenario would be extremely difficult.
While the separate gateway STP approach illustrated in FIG. 1 is functional, it is at the same time inefficient with regard to STP resource requirements. That is, a network operator that provides service in a number of countries is not able to consolidate STP processing for the different countries into a single STP node. Instead, the operator in each country must install and maintain a separate STP to allow for the routing of country specific ITU-N signaling traffic without the duplicate point code conflicts described above. Each STP must also use ITU-I point codes to route messages between national networks.
While other solutions to this duplicate point code dilemma have been proposed and implemented, they each have significant problems. For instance, one solution involves incorporating a system identifier (SID) within a signaling message to distinguish between messages with the same point codes destined for different signaling points in different national networks. However, it has been proven that SID codes can also present numbering conflicts between countries. Wireless systems use five-digit SID codes to uniquely identify each operator's network and market, and these SID code ranges are allocated internationally by the International Forum on AMPS Standards Technology (IFAST) and in North America by CIBERNET. In keeping with the SID concept, national network operators are supposed to use codes designated by their national telecommunications authority within the range specified for their country. However, as international coordination of SID assignments is relatively recent, some SIDs are in use by operators in more than one country. Consequently, a network operator with a large base of embedded non-IFAST SIDs must either find a solution to potential SID conflict issues or re-program mobile handsets. In other words, the SID solution has simply created another network identifier that has no guarantee of uniqueness, which presents the same core problem as duplicate national point codes.
Therefore, what is needed is a system and method of enabling a single STP or STP-like routing node to simultaneously route signaling messages between multiple national networks that employ duplicate point codes.